We previously isolated a cell line (JR) from a patient with aplastic anemia that produces HTLV II. We are continuing to characterize this cell line and the virus that it produces in order to determine whether its association with aplasia is due to a unique characteristic of this isolate. We analyzed the proteins produced by JR cells by Western blot analysis of JR cells and purified virus and compared these results with standard HTLV II cells and viruses. PCR based sequence analysis of DNA fragments amplified from JR cells were prepared and sequenced. These results show extensive homology between JR and known HTLV II isolates. We are cloning JR virus. Eco RI fragments from genomic DNA of JR cells were prepared and cloned in a lambda vector. The library was screened using subclones of HTLV II Mo viral DNA. Positive clones were identified and partially sequenced. Our results indicate that there is extensive homology between JR and known HTLV II isolates. We are continuing our efforts to clone this virus. We have analyzed sera from other aplastic anemia patients for antibodies to HTLV I/II. One additional reactive sample was detected. We are currently studying whether this person was infected with HTLV.